The present application is at least generally related to the field of underground directional drilling and, more particularly, to a directional drilling target steering system, apparatus and associated method.
A boring tool is well-known as a steerable drill head that can carry sensors, transmitters and associated electronics. The boring tool is usually controlled through a drill string that is extendable from a drill rig. The drill string is most often formed of drill pipe sections, which may be referred to hereinafter as drill rods, that are selectively attachable with one another for purposes of advancing and retracting the drill string. Steering is often accomplished using a beveled face on the drill head. Advancing the drill string while rotating should result in the boring tool traveling straight forward, whereas advancing the drill string with the bevel oriented at some fixed angle should result in deflecting the boring tool in some direction.
One prior art approach for guiding the boring tool involves what can be referred to as a homing or steering system. Generally, such a system generates steering commands that should ultimately result in the boring tool being steered to a target. Applicants recognize, however, that prior art systems have been limited in large measure to an uninterpreted display of the actual steering commands to an operator. Based solely on access to the steering commands, the skill of the operator becomes paramount in terms of correct interpretation or translation of the steering commands into drill rig machine actuations for successful guidance of the boring tool to the target location. For example, the operator has been relied on to gather information from relatively diverse sources and locations in order to properly provide input actuations to the drill rig which cause the boring tool to respond appropriately to a given steering command.
Another prior art approach for guiding the boring tool involves what can be referred to as a target path or bore plan. Such a bore plan is typically predetermined in advance of the actual horizontal directional drilling operation. The bore plan can be customized to accommodate any set of circumstances such as, for example, avoiding pre-existing utilities, structures, obstacles, and/or property boundaries. An example of such an advanced system is seen in commonly owned U.S. Pat. No. 6,035,951 (hereinafter, the '951 patent), which is hereby incorporated by reference, and described in detail with reference to FIGS. 17-19 of the patent. Each of the latter figures includes a steering coordinator 630 that can be used by the operator to guide the boring tool along a target path that is designated by the reference number 626 in FIG. 17 of the '951 patent. During drilling, the operator must translate the steering coordinator display into machine actuations to be applied to the drill rig to return the boring tool to the target path responsive to deviations therefrom and to advance the boring tool along the target path.
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.